U.S. patent application number 11/937158 was filed with the patent office on 2008-10-23 for cleaning apparatus and image forming apparatus.
This patent application is currently assigned to CANON KABUSHIKI KAISHA. Invention is credited to Tetsuro Awaya.
Application Number | 20080260439 11/937158 |
Document ID | / |
Family ID | 39480234 |
Filed Date | 2008-10-23 |
United States Patent
Application |
20080260439 |
Kind Code |
A1 |
Awaya; Tetsuro |
October 23, 2008 |
CLEANING APPARATUS AND IMAGE FORMING APPARATUS
Abstract
A cleaning device includes a cleaning blade for contacting to a
rotatable image bearing member and removing toner from the image
bearing member; an auxiliary cleaning member, disposed upstream of
the cleaning blade with respect to a rotational direction of the
image bearing member, for assisting cleaning operation of the
cleaning blade; and a sheet contacted to the auxiliary cleaning
member and to a surface of the cleaning blade which is remote from
the image bearing member.
Inventors: |
Awaya; Tetsuro; (Tokyo,
JP) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
US
|
Assignee: |
CANON KABUSHIKI KAISHA
Tokyo
JP
|
Family ID: |
39480234 |
Appl. No.: |
11/937158 |
Filed: |
November 8, 2007 |
Current U.S.
Class: |
399/349 |
Current CPC
Class: |
G03G 21/0029 20130101;
G03G 21/0035 20130101; G03G 2215/00021 20130101 |
Class at
Publication: |
399/349 |
International
Class: |
G03G 21/00 20060101
G03G021/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 15, 2006 |
JP |
2006-308894 |
Claims
1. A cleaning device comprising: a cleaning blade for contacting to
a rotatable image bearing member and removing toner from the image
bearing member; an auxiliary cleaning member, disposed upstream of
said cleaning blade with respect to a rotational direction of said
image bearing member, for assisting a cleaning operation of said
cleaning blade; and a sheet contacted to said auxiliary cleaning
member and to a surface of said cleaning blade which is remote from
said image bearing member.
2. A cleaning blade according to claim 1, wherein said auxiliary
cleaning member is rotatable, and a rotational direction of said
auxiliary cleaning member is opposite to the rotational direction
of said image bearing member.
3. A cleaning blade according to claim 1, wherein said auxiliary
cleaning member includes a fur brush roller.
4. A cleaning blade according to claim 4, further comprising a
removing member for entering into said fur brush removing the toner
deposited on said fur brush.
5. A cleaning blade according to claim 4, further comprising a
removing member for entering into said fur brush and removing the
toner deposited on said fur brush, wherein an entering amount of
said removing member into said fur brush is larger than an entering
amount of said sheet into said fur brush.
6. A cleaning blade according to claim 1, wherein a contact portion
between said cleaning blade and said image bearing member is below
a contact portion between said auxiliary cleaning member and said
image bearing member.
7. A cleaning blade according to claim 1, wherein said sheet
material moves away from said cleaning blade by a pressure of the
toner accumulated between said image bearing member and said sheet
material, and the toner falls through a gap provided between said
cleaning blade and said sheet material by the pressure.
8. A cleaning blade according to claim 7, further comprising a
supporting member for supporting said sheet material, wherein said
supporting member is provided with a hole portion through which the
toner falls into a toner accommodating portion.
9. An image forming apparatus comprising: a rotatable image bearing
member; a cleaning blade for contacting to said rotatable image
bearing member and removing toner from said image bearing member;
an auxiliary cleaning member, disposed upstream of said cleaning
blade with respect to a rotational direction of said image bearing
member, for assisting a cleaning operation of said cleaning blade;
a sheet contacted to said auxiliary cleaning member and to a
surface of said cleaning blade which is remote from said image
bearing member.
10. An apparatus according to claim 9, wherein said auxiliary
cleaning member is rotatable, and a rotational direction of said
auxiliary cleaning member is opposite to the rotational direction
of said image bearing member.
11. An apparatus according to claim 9, wherein said auxiliary
cleaning member is a fur brush roller.
12. An apparatus according to claim 10, further comprising a
removing member for entering into said fur brush removing the toner
deposited on said fur brush.
13. An apparatus according to claim 10, further comprising a
removing member for entering into said fur brush and removing the
toner deposited on said fur brush, wherein an entering amount of
said removing member into said fur brush is larger than an entering
amount of said sheet into said fur brush.
14. An apparatus according to claim 9, wherein a contact portion
between said cleaning blade and said image bearing member is below
a contact portion between said auxiliary cleaning member and said
image bearing member.
15. An apparatus according to claim 1, wherein said sheet material
moves away from said cleaning blade by a pressure of the toner
accumulated between said image bearing member and said sheet
material, and the toner falls through a gap provided between said
cleaning blade and said sheet material by the pressure.
16. An apparatus according to claim 15, wherein said supporting
member is provided with a hole portion through which the toner
falls into a toner accommodating portion.
Description
FIELD OF THE INVENTION AND RELATED ART
[0001] The present invention relates to a cleaning apparatus for an
image forming apparatus, such as a copying machine or a printer,
which is of the transfer type. More specifically, it relates to a
cleaning apparatus for removing the developer remaining on the
image bearing member, such as an electrophotographic photosensitive
member, of an image forming apparatus after the transfer of a
developer image formed on the image bearing member. It also relates
to an image forming apparatus employing the cleaning apparatus.
[0002] The inventors of the present invention had proposed a
cleaning apparatus, the cleaning performance of which remains at a
satisfactory level for a long time. This cleaning apparatus is
disclosed in Japanese Laid-open Patent Application 2004-271968.
[0003] This cleaning apparatus has a cleaning blade, which is in
contact with the image bearing member to remove the developer
(which hereafter may be referred to as residual toner) remaining on
the image bearing member. It also has an auxiliary cleaning member,
which is in contact with the image bearing member, and is rotates
to remove the residual toner on the abovementioned image bearing
member. In terms of the rotational direction of the image bearing
member, the auxiliary cleaning member is on the upstream side of
the cleaning blade. The auxiliary cleaning member scrapes and stirs
the transfer residual toner, and also, ensures that the image
bearing member is always coated with a preset (appropriate) amount
of toner. In terms of the rotational direction of the image bearing
member, the cleaning blade and auxiliary cleaning member are
positioned so that the area of contact between the cleaning blade
and image bearing member, and the area of contact between the
auxiliary cleaning member and image bearing member, fall within
90.degree. from the lowest point of the peripheral surface of the
image bearing member, that is, the lower of the intersections of
the direction of gravity and the peripheral surface of the image
bearing member. Further, they are positioned so that the area of
contact between the cleaning member and image bearing member does
not overlap with the sweeping range of the auxiliary cleaning
member, in terms of the direction of gravity.
[0004] In the case of this cleaning apparatus, as the transfer
residual toner is removed from the image bearing member by the
auxiliary cleaning member, the removed toner falls in the direction
of gravity due to its own weight, and accumulates below the image
bearing member, without resettling on the image bearing member.
Further, as the transfer residual toner is removed from the image
bearing member by the cleaning blade, the removed toner falls in
the direction of gravity due to its own weight, and accumulates
below the image bearing member, without resettling on the image
bearing member. Thus, the amount by which toner is re-coated on the
image bearing member by the auxiliary cleaning member remain
stable. The re-coated toner, which is stable in amount, serves as
lubricant, contributing to the reduction in the buckling of the
cleaning blade, occurrences of low frequency vibrations (noises),
etc. Therefore, this cleaning apparatus remains satisfactory in
cleaning performance for a long time.
[0005] The cleaning blade is likely to buckle, or vibrate at a low
frequency, immediately after an image forming apparatus is set up
for an image forming operation, or the cartridge (inclusive of
cleaning apparatus) in the image forming apparatus is replaced with
a fresh one. Therefore, in order to minimize the buckling of the
cleaning blade, or the occurrence of low frequency vibrations, a
preset (appropriate) amount of toner is placed as lubricant along
the cleaning edge of the cleaning blade, before the shipment of an
image forming apparatus or a cartridge from a factory.
[0006] It is possible, however, that during the shipment, the
abovementioned preset amount of toner will fall (will be lost) due
to the vibrations or the like which occur during the distribution
of the apparatus or cartridge. Therefore, in spite of the placement
of the preset (appropriate) amount of toner along the cleaning edge
of the cleaning blade, it is still possible that the cleaning blade
will buckle or vibrate at a low frequency (make low frequency
noises), immediately after an image forming apparatus is set up for
an image forming operation, or the cartridge in the image forming
apparatus is replaced with a fresh one.
[0007] As one of the means for preventing the above described
problem, it is possible to form a closed space by the peripheral
surface of the drum, the cleaning blade, and a roller-shaped brush,
and retain a certain amount of toner in this closed space. This
solution, however, suffers from the following problem: If the
amount of the toner retained in the auxiliary cleaning member is
small, the toner in the closed space adheres to the auxiliary
cleaning member and/or is scraped away by the auxiliary cleaning
member as the auxiliary cleaning member is rotated. Therefore, the
amount by which toner remains in the closed space is unstable,
making it possible that the cleaning blade will buckles and/or
erratically vibrate or make low frequency noises, which is one of
the causes of the formation of an unsatisfactory image.
[0008] Japanese Laid-open Patent Application H11-1611256 discloses
another solution to the abovementioned problem. According to this
application, the back side of the cleaning blade is provided with a
piece of plate so that toner is retained along the cleaning edge of
the cleaning blade. In the case of this structural arrangement,
however, the amount by which toner is retained along the cleaning
edge of the cleaning blade is affected by the amount of the
transfer residual toner, and therefore, the amount by which toner
remains along the cleaning edge is unstable.
[0009] Japanese Laid-open Patent Application 2005-258044 discloses
another solution to the above described problem. According to this
application, unlike the preceding solutions, the cleaning apparatus
is provided with a sleeve on which a magnetic brush is formed. In
terms of the rotational direction of the image bearing member, the
sleeve is on the upstream side of the cleaning blade. Further, the
cleaning apparatus is provided with a member for accumulating toner
on the back side of the cleaning blade. This member is positioned
to make no contact with the sleeve.
[0010] This structural arrangement is also problematic in that, as
copies which are low in image ratio are continuously produced by a
substantial number, not only does the amount by which toner reaches
the cleaning blade reduce, but also, the toner having accumulated
along the cleaning edge adheres to the magnetic brush, making
unstable the amount by which toner remains along the cleaning edge
of the cleaning blade.
SUMMARY OF THE INVENTION
[0011] The primary object of the present invention is to stabilize
the amount by which toner remains along the cleaning edge of the
cleaning blade.
[0012] According to an aspect of the present invention, there is
provided a cleaning device comprising a cleaning blade for
contacting to a rotatable image bearing member and removing toner
from the image bearing member; an auxiliary cleaning member,
disposed upstream of said cleaning blade with respect to a
rotational direction of said image bearing member, for assisting
cleaning operation of said cleaning blade; and a sheet contacted to
said auxiliary cleaning member and to a surface of said cleaning
blade which is remote from said image bearing member.
[0013] These and other objects, features, and advantages of the
present invention will become more apparent upon consideration of
the following description of the preferred embodiments of the
present invention, taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a sectional view of the drum cartridge portion of
the image forming apparatus in one of the preferred embodiments of
the present invention.
[0015] FIG. 2 is an enlarged sectional view of the cleaning
apparatus portion of the image forming apparatus shown in FIG.
1.
[0016] FIG. 3 is an enlarged sectional view of the cleaning
apparatus portion of the image forming apparatus, in which the
excessive toner is being discharged through the hole which the base
plate for supporting the backup sheet has.
[0017] FIG. 4 is a perspective view of the drum, cleaning blade,
and backup sheet.
[0018] FIG. 5 is a sectional view of the image forming apparatus in
the abovementioned preferred embodiment of the present invention,
showing the general structure of the apparatus.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0019] Hereinafter, the image forming apparatus in accordance with
the present invention will be described with reference to the
appended drawings.
Embodiment
(1) General Structure of Image Forming Apparatus
[0020] FIG. 5 is a schematic sectional view of the image forming
apparatus in this embodiment, showing the general structure of the
apparatus. FIG. 1 is an enlarged view of the drum cartridge portion
of the image forming apparatus shown in FIG. 5. The image forming
apparatus in this embodiment is an electrophotographic copying
machine of the so-called single drum type, that is, an image
forming apparatus which employs a single photosensitive member, and
synthetically forms a full-color image on the photosensitive member
by repeating an image forming operation for forming a monochromatic
image, four times per full-color image.
[0021] This copying machine has an image forming portion A and an
image reading portion B (digital color image reading portion). The
image forming portion A is provided with an image forming portion
proper and a paper feeding mechanism portion. The image reading
portion B is above the image forming portion A.
[0022] An original, for example, a color original (full-color
image), is placed on an original placement platen 21 of the image
reading portion B, with the image bearing surface of the original
facing downward, so that the original aligns with a preset
referential line, or the like. Then, the original is covered with
an original pressing plate 22. The original placement platen 21 is
formed of transparent glass.
[0023] There is a first scanning unit 25 under the original
placement platen 21. The first scanning unit 25 has an original
illuminating lamp 23 and a first mirror 24. As a copy start button
is pressed, the first scanning unit 25 is driven so that it moves
along the bottom surface of the original placement platen 21 at a
preset velocity V. Further, a second scanning unit 28 having second
and third mirrors 26 and 27 is driven so that it also moves along
the bottom surface of the original placement platen 21 at a
velocity of V/2, that is, half the velocity at which the first
scanning unit 25 is moved. As the first and second scanning units
25 and 28 are driven as described above, the bottom surface of the
color original on the original placement platen 21 is scanned so
that the pictorial information of the original is obtained by a
full-color sensor unit 29; the beam of light projected from the
original illuminating lamp 23 and reflected by the original is
separated into beams of light of primary colors, and each of the
beams of light of primary colors is photoelectrically read
(converted into electrical signals). Then, the thus obtained
electric signals are processed by an image processing portion, and
are inputted into a control unit R of the image forming portion
A.
[0024] The image forming portion A is equipped with an image
bearing member, which is an electrophotographic photosensitive
member 1 in the form of a drum with an external diameter of 60 mm
(hereafter, electrophotographic photosensitive drum will be
referred to simply as drum). The drum 1 is rotationally driven at a
preset peripheral velocity in the clockwise direction, that is, the
direction indicated by an arrow mark in the drawing. As the drum 1
is rotationally driven, the peripheral surface of the drum 1 is
uniformly charged to preset polarity and potential level by a
primary charge roller 2, as a charging means, which is 10 mm in
external diameter. Then, the charged portion of the peripheral
surface of the drum 1 is exposed by a laser unit 3 (laser scanner),
as an exposing unit; it is scanned by the beam of laser light
projected by the laser unit 3 while being modulated according to
the picture information. As a result, an electrostatic latent image
(pattern of exposure) is formed on the peripheral surface of the
drum 1. More specifically, the laser unit 3 outputs a beam of laser
light while modulating it with the picture signals sent from the
control unit R. As the uniformly charged portion of the peripheral
surface of the drum 1 is scanned (exposed) by this beam of light,
an electrostatic latent image (pattern of exposure) is effected on
the peripheral surface of the drum 1. The electrostatic latent
image is developed by the developer (which hereafter may be
referred to as toner) in the black developing device K, yellow
developing device Y, magenta developing device M, or cyan
developing device C of a developer unit 4 of the rotary type.
[0025] The abovementioned four developing devices K, Y, M, and C
are mounted in a rotary 4b (rotational member), which is rotatably
supported by a shaft 4a, making it possible to move any of the four
developing devices into the development position, that is, the
position in which it can develop the electrostatic latent image on
the drum 1, by rotating the rotary 4b in a controlled manner. The
electrostatic latent image on the drum surface is developed by the
toner in the developing device having moved into the development
position. The abovementioned charging means 2, exposing means 3,
and developing means 4 make up the image forming means for forming
a toner image on the drum 1.
[0026] After the formation of a toner image on the drum 1, the
toner image is transferred (primary transfer) onto an intermediary
transfer belt 6 (which hereafter will be referred to as belt) in a
primary transfer station T1. The belt 6 is a member of an
intermediary transfer unit 5, onto which a toner image is
temporarily transferred. It is a flexible and endless belt, and is
formed of a dielectric material. It is supported by a primary
transfer roller 7, an auxiliary second transfer roller 8, and a
tension roller 9, being thereby stretched around them. The primary
transfer roller 7 is kept pressed against the drum 1 with the
presence of the belt 6 between the roller 7 and drum 1. The
interface between the drum 1 and belt 6 is the primary transfer
station T1. As the auxiliary secondary transfer roller 8 is
rotationally driven, the belt 6 is circularly driven by the roller
8 at a peripheral velocity, which matches the peripheral velocity
of the drum 1, in the counterclockwise direction, that is, the
direction indicated by an arrow mark. As a preset primary transfer
bias is applied to the primary transfer roller 7, the toner image
on the drum 1 is electrostatically transferred onto the belt 6 in a
manner of being peeled away from the peripheral surface of the drum
1.
[0027] After the transfer of the toner image onto the surface of
the belt 6, the drum surface is cleaned by a cleaning apparatus 10
(transfer residual toner on the peripheral surface of the drum 1 is
removed by the cleaning apparatus 10) so that the peripheral
surface of the drum 1 is repeated used for an image forming
operation. The cleaning apparatus 10 will be described in detail in
Section 2.
[0028] In the case of the image forming apparatus in this
embodiment, the abovementioned drum 1 and primary transfer roller
2, and cleaning apparatus 10 are integrated in the form of an image
formation unit Q (process cartridge Q), which is removably
mountable in the main assembly A of the image forming
apparatus.
[0029] The main assembly A is provided with a secondary transfer
roller 11, which is positioned so that it can be placed in contact
with, or separated from, the portion of the belt 6, which is in
contact with the auxiliary secondary transfer roller 8. As the
secondary transfer roller 11 is placed in contact with the portion
of the belt 6, which is in contact with the auxiliary secondary
transfer roller 8, a secondary transfer station T2 is formed
between the belt 6 and secondary transfer roller 11.
[0030] The main assembly A is also provided with a belt cleaner 12,
which is positioned so that it can be placed in contact with, or
separated from, the portion of the belt 6, which is in contact with
the tension roller 9.
[0031] When the image forming apparatus is in the full-color image
formation mode, the combination of the step for forming a toner
image on the drum 1 and the step for transferring (primary
transfer) the toner image from the drum 1 onto the belt 6 is
sequentially carried out four times, once for each of the four
primary colors, that is, yellow, magenta, cyan, and black colors,
in the list order. As a result, four toner images, which are
different in color, are transferred in layers onto the surface of
the belt 6, synthetically effecting a single unfixed full-color
toner image. Incidentally, the order in which the four toner
images, different in color, are to be formed does not need to be
limited to the abovementioned one.
[0032] During the primary transfer, that is, while a toner image is
transferred from the drum 1 onto the belt 6, the secondary transfer
roller 11 and belt cleaner 12 are kept separated from the belt 6 so
that the toner image (images) having just been transferred (primary
transfer) onto the belt 6 is not disturbed.
[0033] In synchronism with the completion of the transfer (primary
transfer) of the last color toner image onto the belt 6, that is,
the completion of the synthetic formation of an unfixed full-color
toner image (based on four primary colors) on the belt 6, a control
is executed so that the secondary transfer roller 11 is placed in
contact with the belt 6, forming thereby the secondary transfer
station T2.
[0034] Meanwhile, sheets of recording medium S (which hereafter
will be referred to simply as recording mediums S) are fed from the
sheet feeder cassette selected from among first to fourth sheet
feeder cassettes 41-44 of the sheet feeding system, into the main
assembly A, while being separated one by one. Then, each recording
medium S is introduced into the abovementioned secondary transfer
station T2, that is, the nip between the secondary transfer roller
11 and belt 6, through a sheet conveyance path which includes a
pair of registration rollers 13, with a preset control timing.
Incidentally, the main assembly A is also provided with a manual
feeder portion 45 (tray), through which recording mediums S can be
manually fed, one by one, into the apparatus main assembly A, so
that each recording medium S is introduced into the nip T2 through
a sheet conveyance path which includes the pair of registration
rollers 13 with the preset control timing.
[0035] Each recording medium S is conveyed through the secondary
transfer station T2 while remaining pinched by the belt 6 and
secondary transfer roller 11. As the recording medium S is conveyed
through the secondary transfer station T2, the unfixed four
monochromatic toner images, on the belt 6, which are different in
color and synthetically make up the single unfixed full-color
image, are transferred together (secondary transfer) onto the
recording medium S. During this transfer, or the secondary
transfer, a preset bias (secondary transfer bias) is applied to the
secondary transfer roller 11. After being conveyed out of the
secondary transfer station T2, the recording medium S is separated
from the surface of the belt 6, and is introduced into a fixing
device 14, which employs a heat roller. In the fixing device 14,
the recording medium S and the four monochromatic toner images
thereon are subjected to heat and pressure. As a result, the
yellow, magenta, cyan, black toner images, which have just been
transferred in layers onto the recording medium S, are fixed to the
recording medium while being mixed. Consequently, a full-color
print is yielded. After being conveyed out of the fixing device 14,
the recording medium S is discharged by a pair of discharge roller
15 onto a delivery tray 16.
[0036] When the image forming apparatus in the black-and-white
mode, only a black toner image is formed on the drum 1, and is
transferred (primary transfer) onto the belt 6. Then, the black
toner image is transferred (secondary transfer) from the belt 6
onto the recording medium S. Then, the recording medium S is
introduced into the fixing device 14.
(2) Drum Cartridge Q and Cleaning Apparatus 10
[0037] Next, referring to FIGS. 1-4, the drum cartridge Q, which is
an image formation unit, and the cleaning apparatus 10, will be
described regarding their structures. FIG. 2 is an enlarged view of
the cleaning apparatus portion of FIG. 1. FIG. 3 is an enlarged
sectional view of the cleaning apparatus portion of the image
forming apparatus, in which the excessive toner is being discharged
through the hole which the base plate for supporting the backup
sheet has. FIG. 4 is a perspective view of the drum, cleaning
blade, and backup sheet.
[0038] The drum cartridge Q in this embodiment is an assembly made
up of the drum 1, primary charge roller 2, and cleaning apparatus
10, which are integrally placed in a shell (cartridge) so that they
can be removably mounted together into the apparatus main assembly
A. As the cartridge Q is mounted into the apparatus main assembly
A, it becomes mechanically and electrically connected to the main
assembly A of the copying machine, making it possible for the image
forming apparatus to carry out an image forming operation. That is,
it becomes possible for the drum 1 to be rotationally driven by the
driving means of the apparatus main assembly A. The primary charge
roller 2 is rotated by the rotation of the drum 1. Further, it
becomes possible for the electrically conductive brushing roller 35
(fur brush in the form of roller) of the cleaning apparatus 10,
which is an auxiliary cleaning member, to be rotationally driven by
the driving means of the apparatus main assembly A. Moreover, the
electrically conductive brushing roller 35 becomes electrically
connected (grounded) to the housing of the apparatus main assembly
A.
[0039] The drum 1, charge roller 2, and cleaning apparatus 10 are
located in the first portion 31, that is, the drum container
portion, of the shell of the cartridge. The opening of the drum
container portion 31 is covered with a drum cover 32, as the second
portion of the cartridge shell, which is joined with the first
portion 31 of the cartridge shell. In other words, the first and
second portions of the cartridge shell make up waste toner storage
33.
[0040] The drum 1 is rotatably supported by the drum container
portion 31 of the cartridge shell, with the interposition of
bearings. Also, the charge roller 2 is rotatably supported by the
drum container portion 31 with the interposition of bearings. The
charge roller 2 is protected with the charger roller cover 31a,
which is integral with the drum container portion 31.
[0041] The cleaning apparatus 10 has a cleaning blade 34 and the
electrically conductive brush 35. The cleaning blade 34 is formed
of rubber. The electrically conductive brush 35 is in the form of a
roller, and is 18 mm in external diameter.
[0042] The cleaning blade 34 is firmly attached to the edge of a
base plate 34a (metallic supporting plate), being thereby supported
by the base plate 34a, and the base plate 34a is firmly attached to
the drum container portion 31 of the cartridge shell so that the
cleaning edge of the cleaning blade 34 is on the upstream side,
relative to the base portion of the blade 34, in terms of the
rotational direction of the drum 1.
[0043] The electrically conductive brushing roller 35 is rotatably
supported by the drum container portion 31 of the cartridge shell,
with the interposition of bearings. It is in contact with the drum
1, on the upstream side, relative to the area of contact between
the cleaning blade 34 and drum 1, in terms of the rotational
direction of the drum 1. The electrically conductive brushing
roller 35 is rotationally driven in such a direction that the
movement of the peripheral surface of the drum 1 in the area of
contact between the drum 1 and brushing roller 35 is opposite in
direction to the movement of the cleaning edges of the bristles of
the brushing roller 35. Further, the electrically conductive
brushing roller 35 is electrically connected (grounded) to the
housing of the image forming portion A.
[0044] The cleaning apparatus 10 is provided with an elastic sheet
36 (which hereafter will be referred to as backup sheet), which is
formed of urethane and is roughly 100 .mu.m in thickness. At least
a part of the backup sheet 36 is in contact with the opposite
surface (back surface) of the cleaning blade 34 from the drum 1.
The backup sheet 36 is firmly attached to a base plate 36a, as a
backup sheet supporting member, being thereby supported by the base
plate 36a. The base plate 36a is formed of SUS, and is roughly 0.2
mm in thickness. It is accurately positioned relative to the base
plate 35a. The base plate 36a is firmly attached to the drum
container portion 31 of the cartridge shell, together with the base
plate 35a of the cleaning blade 35.
[0045] The base plate 36a of the backup sheet 36 is provided with a
hole 36b for discharging excessive toner. The backup sheet 36 is
disposed in contact with the electrically conductive brushing
roller 35 so that its opposite edge portion from the base plate 36a
extends beyond the cleaning edge of the cleaning blade 34 toward
the electrically conductive brushing roller 35. In this embodiment,
the backup sheet 36 is disposed so that the distance H by which the
backup sheet 36 apparently intrudes into the electrically
conductive brushing roller 35 is roughly 1 mm. This distance H is
obtained by measuring in length (depth) the portion of the backup
sheet 36, which is on the inward side of the tip circle of the
electrically conductive brushing roller 35, when the roller 35 is
stationary.
[0046] Further, the cleaning apparatus 10 is provided with a
scraper 37, which is a toner removing member (brush refreshing
member) for removing the toner having adhered to the brushing
roller 35. The scraper 37 is placed in contact with the
electrically conductive brushing roller 35. It is an elastic sheet,
which is attached to a scraper attachment base member 37a by the
portion opposite to its scraping edge, with the scraping edge
portion apparently intruding by roughly 2 mm (apparent amount of
intrusion G) into the electrically conductive brushing roller 35,
in terms of the radius direction of the brushing roller 35. The
scraper attachment base member 37a is firmly attached to the drum
container portion 31 of the cartridge shell so that it precisely
positioned. As the electrically conductive brushing roller 35 is
rotated, the bristles of the brushing roller 35 are stroked and
scraped by the scraper 37. Therefore, the toner having entered the
spaces among the bristles of the brushing roller 35 as it is
recovered by the brushing roller 35 is expelled out of the brushing
roller 35. Further, the cleaning apparatus is provided with a cover
sheet 38 which covers the electrically conductive brushing roller
35 to prevent the toner having been expelled from the brushing
roller 35, from reentering the spaces among the bristles of the
brushing roller 35. The cover sheet 38 is attached to a cover sheet
attachment base 38a, which is firmly attached to the drum container
portion 31 of the cartridge shell so that it is precisely
positioned.
[0047] Moreover, the cleaning apparatus 10 is provided with an
elastic sheet 39 (squeezing sheet) for preventing toner from
leaking through the gap between the drum 1 and the drum container
portion 31 of the cartridge shell. In terms of the rotational
direction of the drum 1, the elastic sheet 39 is located upstream
of the electrically conductive brushing roller 35. It is firmly
attached to the drum container portion 31 of the cartridge shell by
its base portion so that its functional edge portion is placed in
contact with the drum 1.
[0048] Referring to FIG. 1, Line X-X and Line Y-Y are the
horizontal and vertical lines (hypothetical lines) which coincide
with rotational axis of the drum 1 when the drum cartridge Q is in
its image forming position in the main assembly A of the copying
machine. The downward direction parallel to Line Y-Y (vertical
line) is the direction of gravity. In this embodiment, the primary
charge roller 2 is positioned in the cartridge Q so that when the
cartridge Q is in its image forming position in the apparatus main
assembly A, the primary charge roller 2 is under the drum 1 (and
also, in the adjacencies of Line X-X (vertical line)). The cleaning
blade 34 is disposed in the cartridge Q so that when the cartridge
Q is in its image forming position in the apparatus main assembly
A, the point of contact between the cleaning blade 34 (cleaning
edge) and drum 1 is upstream of the lowest point of the drum 1, by
roughly 40.degree., in terms of the rotational direction of the
drum 1. Next, referring to FIG. 3, the electrically conductive
brushing roller 35 is disposed in the cartridge Q so that when the
cartridge Q is in its image forming position in the apparatus main
assembly A, the point a, that is, the point of contact between the
electrically conductive brushing roller 35 and drum 1, is upstream
of the point b, that is, the point of contact between the cleaning
blade 34 and drum 1, by roughly 5.degree. (FIG. 1) in terms of the
rotational direction of the drum 1.
[0049] Next, referring to FIG. 3, a closed space E will be
described. The closed space E is a space formed along the
peripheral surface of the drum 1, between the abovementioned point
b, that is, the point of contact between the cleaning blade 34 and
drum 1 and the point a, that is, the point at which the
electrically conductive brushing roller 35 begins to contact the
peripheral surface of the drum 1. On the opposite side of the
closed space E from the peripheral surface of the drum 1, the
backup sheet 36 is in contact with the electrically conductive
brushing roller 35. In other words, the closed space E is formed by
the portion of the peripheral surface of the drum 1, which is
between the abovementioned points a and b, the portion of the
surface of the cleaning blade 34, which is between the point b and
a point c, that is, the point of contact between the cleaning blade
34 and backup sheet 36, the portion of the backup sheet 36, which
is between the point c and a point d, that is, the point at which
the peripheral surface (pitch circle) of the electrically
conductive brushing member 35 begins to contact the backup sheet
36, and the portion of the peripheral surface (pitch circle) of the
brushing member 35, which is between the points d and a. The
cleaning apparatus 10 in this embodiment is structured so that the
backup sheet 36 extends beyond the cleaning edge of the cleaning
blade 34 and is in contact with the electrically conductive
brushing roller 35.
[0050] This closed space E is used as a toner storage. That is,
before the drum cartridge Q is shipped out of a drum cartridge
factory, a preset amount of toner t (FIG. 2) is stored as lubricant
in this closed space E.
[0051] The above described closed space E functions as a storage in
which the preset amount of toner can be reliably stored. Therefore,
by storing the preset amount of toner in this closed space, it is
possible to prevent the toner from disappearing (falling) from the
cleaning edge of the cleaning blade 34 due to the vibrations or the
like which occur during the distribution of the cartridge Q.
Therefore, this embodiment of the present invention can prevent the
problem that the cleaning blade 34, as the drum cleaning member,
buckles, and/or vibrates at a low frequency, right after the image
forming apparatus is set up for an image forming operation, or
right after the cartridge Q in the image forming apparatus main
assembly is replaced with a brand-new one, or the like
problems.
[0052] Further, the electrically conductive brushing roller 35 is
prevented by the backup sheet 36 from contacting the toner located
along the cleaning edge of the cleaning blade 34. Therefore, the
toner accumulated in the closed space E during an image forming
apparatus is not absorbed by the electrically conductive brushing
roller 35; it is ensured that a sufficient amount of toner always
remains as lubricant along the cleaning edge of the cleaning blade
34.
[0053] The residual toner, or the toner remaining on the peripheral
surface of the drum 1 after the primary transfer, that is, the
toner which failed to be transferred onto the belt 6 during an
image forming operation, is first recovered by the rotating
electrically conductive brushing member 35, which is the auxiliary
drum cleaning member. Then, the toner recovered by the electrically
conductive brushing roller 35 is stroked out of the electrically
conductive brushing roller 35 by the scraper 37, and falls in the
direction of gravity due to its own weight, and accumulates in the
waste toner storage portion 33. Designated by an alphabetic
reference ta is the body of toner having accumulated in the waste
toner storage 33.
[0054] As the electrically conductive brushing member 35 is
rotated, the portion of the electrically conductive brushing member
35, which has just been refreshed by the scraper 37, comes again
into contact with the peripheral surface of the drum 1, coating
thereby an appropriate amount of toner on the portion of the
peripheral surface of the drum 1, which is on the upstream side of
the cleaning edge of the cleaning blade 34. Then, the coated toner
is scraped up by the cleaning blade 34, which is on the downstream
side. As the coated toner is scraped up by the cleaning blade 34,
it collects in the closed space E. In other words, the closed space
E from which the toner therein is consumed during an image forming
operation is replenished with toner. Therefore, it is ensured that
a preset (appropriate) amount of toner is always present as
lubricant along the cleaning edge of the cleaning blade 34.
[0055] Further, the cleaning blade 34 and electrically conductive
brushing roller 35 are disposed so that they do not overlap in
terms of the direction of gravity. Therefore, it does not occur
that as the residual toner is scraped away from the cleaning blade
34, it falls onto the electrically conductive brushing roller 35.
Therefore, the amount of the toner in the electrically conductive
brushing roller 35 always remains constant, making it possible to
control the amount by which the peripheral surface of the drum 1 is
re-coated with toner by the electrically conductive brushing roller
35.
[0056] The above described effect is obtained as long as an
structural arrangement is made so that, in terms of the rotational
direction of the drum 1, the point of contact between the cleaning
blade 34 and drum 1, and the point of contact between the
electrically conducive brushing roller 35 and drum 1, are no more
than 90.degree. away from the lowest point of the drum 1 in terms
of the direction of gravity, and also, so that the point of contact
between the cleaning blade 34 and drum 1 does not overlap with the
sweeping area of the electrically conductive brushing roller 35 in
terms of the direction of gravity.
[0057] The refreshing effect of the means for refreshing the
electrically conductive roller 35 can be enhanced by using a sheet
of elastic substance as the material for the scraper 37. The
recovered toner, that is, the toner having entered the spaces among
the bristles of the electrically conductive brushing roller 35, can
be aggressively moved out of the brushing roller 35 by disposing
the scraper 37 formed of a sheet of elastic substance, so that the
scraping edge portion of the scraper 37 apparently intrudes into
the electrically conductive brushing roller 35 by roughly 2 mm in
terms of the radius direction of the roller 35. Further, the
electrically conductive brushing roller 35 is covered by the cover
sheet 38 to prevent the toner, which has just been expelled from
the brushing roller 35 after being recovered by the brushing roller
35, from reentering the spaces among the bristles of the brushing
roller 35. After being expelled from the electrically conductive
brushing roller 35, the toner falls down due to its own weight, and
accumulates in the waste toner storage portion 33.
[0058] Not only does the electrically conductive brushing roller
35, which is grounded to the housing portion of the main assembly A
of the copying machine, remove the electrical charge from the
transfer residual toner, which is the same in potential level as
the peripheral surface of the drum 1, but also, disturbs the
residual toner, assisting thereby the cleaning blade 34 in cleaning
the drum 1.
[0059] In this embodiment, the distance (depth) G of the apparent
intrusion of the scraper 37 into the electrically conductive
brushing roller 35 is roughly 2 mm, and the distance (depth) H of
the apparent intrusion of the free edge portion of the backup sheet
36 into the electrically conductive brushing roller 35 is greater
than roughly 1 mm. Therefore, the toner having accumulated in the
electrically conductive brushing roller 35 does not directly come
into contact with the free edge portion of the backup sheet 36.
Therefore, the damage to the free edge portion of the backup sheet
36 is minimized, ensuring that a preset (appropriate) amount of
toner always remains along the cleaning edge of the cleaning blade
34.
[0060] If an excessive amount of toner happens to enter the above
described closed space E, the excessive toner applies pressure to
the backup sheet 36, causing thereby the backup sheet 36 to
separate from the cleaning blade 34. Therefore, the excessive toner
moves out of the closed space E through the gap between the
cleaning blade 34 and the backup sheet 36, and then, is discharged
in the direction indicated by an arrow mark F in FIG. 3, through
the excessive toner discharge hole 36b, with which the base plate
36a is provided. Therefore, the amount by which toner remains along
the cleaning edge of the cleaning blade 34 remains stable at the
preset (appropriate) level.
[0061] Also in this embodiment, not only is the gap provided
between the cleaning blade 34 and backup sheet 36 made wedge by
slanting the backup sheet supporting surface of the base plate 36a,
relative to the portion of the back surface of the cleaning blade
34, which the backup sheet 36 contacts, but also, the backup sheet
supporting base plate 36a is provided with the excess toner
discharge hole 36b. Therefore, if an excessive amount of toner
happens to enter the above described closed space E, the toner
overflow (excessive toner) travels along the slanted surface of the
base plate 36a, and then, is expelled through the hole 36b.
Therefore, the preset (appropriate) amount of toner always remains
as lubricant along the cleaning edge of the cleaning blade 34.
[0062] In this embodiment, the backup sheet 36 is independent from
the cleaning blade 34. However, the backup sheet 36 may be
integrated with the cleaning blade 34 by directly bonding the
backup sheet 36 to the cleaning blade 34. However, if the backup
sheet 36 is directly bonded to the cleaning blade 34, it is
impossible for the excessive toner to be discharged as it is in
this embodiment. Therefore, the structural arrangement in this
embodiment is preferable.
[0063] The auxiliary cleaning member 35 does not need to be the
electrically conductive brushing roller. That is, it may be an
electrically conductive elastic rubber roller. Further, the
auxiliary cleaning member 35 may be rotated in such a direction
that the peripheral surface (tip circle) of the auxiliary cleaning
member 35 and the peripheral surface of the drum 1 move in the same
direction, in the interface between the auxiliary cleaning member
35 and drum 1.
[0064] The image bearing member 1 may be in the form of a
circularly movable belt. Further, the image bearing member 1 does
not need to be an electrophotographic photosensitive member. That
is, it may be an electrostatically recordable dielectric member, an
intermediary transfer member, or the like.
[0065] The image forming apparatus may be structured so that a
toner image formed on the image bearing member 1 is directly
transferred onto the recording medium S.
[0066] As described above, the present invention can stabilize the
amount by which toner is retained along the line of contact between
the cleaning blade and drum, regardless of the type of the image
formed on the drum.
[0067] While the invention has been described with reference to the
structures disclosed herein, it is not confined to the details set
forth, and this application is intended to cover such modifications
or changes as may come within the purposes of the improvements or
the scope of the following claims.
[0068] This application claims priority from Japanese Patent
Application No. 308894/2006 filed Nov. 15, 2006, which is hereby
incorporated by reference.
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